[tdwg-tapir] DwC extensions

Hannu Saarenmaa hannu at bioshare.com
Mon May 26 12:50:19 CEST 2008

John & Co.

It is good to read that DwC would now be finalised as a TDWG standard.  
When we are promoting biodiversity data sharing, it helps to convince 
new followers when we can unambigously state that we are using real 
agreed standards.

My comments to some of the points
> 1) Is species occurrence in nature and in collections the right scope 
> for the Core?
Occurrence of an organism in nature is the core of the core.

Collection specimens is already a step more specialised, and those 
elements could go to an specimen extension or curatorial extension.

This is more or less already taken care and what is left is mainly 
matter of language.  I always have trouble explaining to field observers 
that they need to use Collector for Observer or Reporter.  It is 
confusing to speak of Collector when no specimen was collected. Same 
with CollectionCode which really is something like CatalogCode or 
> 2) Should the general philosophy of the Core be inclusive or 
> minimalist? What are the characteristics of a concept that allow it to 
> be in the Core? What are the characteristics of a concept that allow 
> it to be added to an existing extension?
Minimalist core but inclusive extensions.
> 3) What are the defining characteristics of a group of related 
> concepts that justify the creation of a new extension? Should 
> extensions be based on abstract conceptual groupings/objects (events, 
> identifications/determinations, places)? Or on special interests 
> (paleo, curation, interaction)? Or on the stability of the concepts 
> (core contains the proven stable concepts, extensions are more volatile)?
I favour an approach where the extensions are created by communities of 
users, such as invasive species, agriculture, forestry, observers, 
botanic gardens, museum collections, etc.  Each of these groups already 
have their own databases where the necessary elements can be found.
> 4) Should there be elements in the Core and extensions to hold GUIDs 
> linking them to instances of related classes of objects, such as an 
> occurrence to a TaxonConceptGUID, or an occurrence to a 
> CoreGatheringGUID? Should every extension have a non-mandatory GUID 
> allowing for the external resolution of the object?
The core now has GlobalUniqueIdentifier, which can be used to resolve to 
the other identifiers for gathering, taxon etc.  But that is tricky, and 
I doubt how many people can really deal with it.  I would probably want 
to add direct GUIDs for those most important linking elements, but 
package them all into a Linking Extension.  In particular we should 
include GUID for the taxonomic concept.  That is because LSIDs are now 
available from SP2000, and probably from some others as well.  Lets 
start using them!

The above also concerns the References Elements that need to be removed 
from the core, IMHO.*..
> 5)
> 6) Is it the right approach to have restrictions on content at the 
> concept definition level?
Only in cases when the restriction stems from mathematical or logical 
rule, then restrict.  For agreed sets of values I would refer to 
community practice.  Communities need to keep such lists, which can 
dynamically be changed as agreed, and without need to update standard 

Regards, Hannu

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